Liquid detergent mixtures for domestic and industrial use such as dishwashing agents, laundry detergents, cleaners, cleaning gels for the sanitary sector and; for cosmetic products such as hair shampoos, shower gels and liquid soaps frequently do not have the desired viscous consistency. The viscous consistency of prior art liquid detergent mixtures is, in any event, disadvantageous from an application aspect, but in particular in relation to products for personal use in skin cleaning, skin care and cosmetics is criticized as unfavorable.
When the viscosity is too low, economical dosage is not exactly simple; the contact and the residence/exposure time on the respective surfaces are too short and, when used by hand in the personal sector, the products tend to drain away between one's fingers.
A multiplicity of thickening agents have therefore been proposed in the prior art for surface-active preparations. For example, U.S. Pat. No. 3,856,711 discloses fatty acid amides based on dialkanolamines such as diethanolamine. However, these thickening agents are no longer acceptable because of the potential nitrosamine formation and the associated carcinogenic potential. It is true that thickening agents based on fatty acids and monoisopropanolamine do not have this disadvantage, but their thickening action only develops at elevated amide concentrations, and such thickening agents attain maximum/optimum thickening action only in the presence of sufficiently large amounts of mineral salts. Large amounts of mineral salts are undesirable from an application viewpoint since high concentrations of mineral salts can cause corrosion problems in storage and produce formulations which are less stable at low temperatures. Typically, the monoisopropanolamides of the fatty acids generally used are pasty or solid, and this is likewise an obstacle in application since the monoisopropanolamides are more energy-intensive to incorporate into formulations.
EP-B-0 574 277 proposes the use of the monoisopropanolamide of isostearic acid as a thickening agent. This disclosure provides an improvement in the thickening properties even at low levels and at reduced mineral salt concentrations. Moreover, the product is liquid and relatively easy to process at room temperature (RT).
This represents a significant advance from an application viewpoint, but these compounds are still in need of improvement with regard to their stability in storage, especially at low temperatures.
This is because it has been determined that, in the course of storage, solid fractions settle out from the initially clear product and form a solid sediment. Before use, the thickening agents of EP-B-0 574 277 have to first be remelted and rehomogenized by intensive stirring. The individual use of both of the decanted clear fraction and the solid fraction is not as effective as if the two are used together.
In addition, this procedure results in an undesirable yield loss and/or additional technical complications for the formulator. Moreover, it is impossible to be confident that the end formulation will not develop storage and/or other problems.
It is accordingly an object of the present invention to avoid these problems of the prior art product and to improve its stability in storage, not only at room temperature, but also at low temperatures.